Polyamide resin composition for sound insulation

ABSTRACT

Disclosed is a polyamide resin composition for sound insulation, which includes a polyamide 66 or polyamide 6 resin, a glass fiber for improving mechanical and heat resistance properties of the composition, and barium sulfate for improving a sound insulation property of the composition. The polyamide resin composition can further include one or more of an antioxidant for preventing deterioration of the composition, a heat resistant stabilizer for improving heat resistance, and a lubricant for reducing friction to improve moldability. The polyamide resin composition thus has excellent mechanical properties, heat resistance, noise and vibration insulation performance, and can further be injection molded to thereby provide weight reduction and allow for the formation of complicated shapes.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No.10-2013-0040585, filed on Apr. 12, 2013, the entire contents of which isincorporated herein for all purposes by this reference.

BACKGROUND

(a) Technical Field

The present invention relates to a polyamide resin composition for soundinsulation that effectively insulates engine sounds and noise generatedin an engine room of a vehicle, and more specifically, to a polyamideresin composition for sound insulation which includes polyamide 66 orpolyamide 6 resins, glass fibers and barium sulfates.

(b) Background Art

A partition of an engine room of a vehicle is a wall disposed betweenthe engine room and a dash board to insulate transfer of noise generatedin the engine room into an interior of the vehicle. The partition, thus,improves the comfort level for passengers in the vehicle.

A partition of an engine room of a vehicle is conventionally made of asteel material. However, the weight of such a steel partition isexcessively large, thus reducing fuel efficiency and ride comfort of thevehicle. Further, it is difficult to manufacture a complicated form fromsuch a steel material.

In attempt to solve the above-described problems, a compositionincluding polypropylene, a glass fiber, and iron oxide (Fe₂O₃) havinghigh specific gravity has been used as a vehicle partition. Such acomposition, is more easily processed than metal, is lightweight, can beprovided in various and simple designs and design effects, and is lessexpensive due to its high productivity. However, it provides inadequatemechanical stiffness, heat resistance and injection moldability.

Generally, since a high-filling material having high specific gravity isuseful for insulating noise and vibration, a filler such as iron oxide(Fe₂O₃, specific gravity: 4 to 4.5) and barium sulfate (BaSO₄, specificgravity: 4 to 4.5) is commonly used to increase the weight of amaterial.

Iron oxide and barium sulfate have a higher specific gravity as comparedto talc or wollastonite (specific gravity: 2.6 to 2.9). Thus, thesefillers are extensively used because a sound insulation property can beimproved by increasing the specific gravity of a plastic material.

However, Moh's hardness of iron oxide is about 7, which is significantlyhigh. Thus, screws and molds of injection molding machines are easilyabraded during extrusion and molding of products which include ironoxide due to the high hardness provided thereby. As such, operation andmaintenance of the injection molding machine for high hardness materialsis costly.

Korean Unexamined Patent Application Publication No. 2010-41588describes a polyamide resin composition for a vehicle engine cover,including a polyamide 6 resin, a glass fiber, carbon nanotube and a heatresistant stabilizer. However, the composition is problematic in that asound insulation property is not sufficient even though heat resistanceis excellent. Further, Japanese Unexamined Patent ApplicationPublication No. 1999-43602 describes a polyamide resin compositionincluding a polyamide resin, a glass fiber and barium sulfate. However,the content of barium sulfate is low, and thus there is a disadvantagein that a sufficient sound insulation property is not provided.

SUMMARY OF THE DISCLOSURE

The present invention provides a polyamide resin composition for soundinsulation, which includes a polyamide 66 or polyamide 6 resin, a glassfiber for improving mechanical and heat resistance properties of thecomposition, and barium sulfate for improving a sound insulationproperty of the composition. According to various embodiments, thecomposition can further include one or more of an antioxidant forpreventing deterioration of the composition, a heat resistant stabilizerfor improving heat resistance, and a lubricant for reducing friction toimprove moldability. The composition of the present invention, thus,provides excellent mechanical properties, heat resistance, noise andvibration insulation performance, degree of freedom in design, andinjection moldability. The present invention further provides apartition for a vehicle fabricated from the present composition, whereinthe partition effectively insulates engine sound generated in an engineroom, and thus provides a more comfortable driving environment.

According to one aspect, the present invention provides a polyamideresin composition for sound insulation comprising about 15 to 20 partsby weight of a glass fiber, and about 45 to 50 parts by weight of bariumsulfate, based on 100 parts by weight of a polyamide 66 or polyamide 6resin.

The glass fiber can be any conventional glass fibers that provide thedesired mechanical and heat resistance properties, and according topreferred embodiments, the glass fiber has an average length of about 1mm to 5 mm and an average diameter of a cross section of about 10 to 13μm.

According to various embodiments, the glass fiber is coated with asilane-based coupling agent. Preferably, a weight of the silane-basedcoupling agent is about 0.1 to 0.3 wt % based on a total weight of theglass fiber.

According to various embodiments, an average diameter of barium sulfateparticles is about 20 to 30 μm.

According to various embodiments, the polyamide resin composition forsound insulation further includes one or more of about 0.3 to 0.5 partsby weight of an antioxidant, about 0.3 to 0.5 parts by weight of a heatresistant stabilizer, and/or about 0.2 to 0.4 parts by weight of alubricant.

According to preferred embodiment, the antioxidant is a mixture of aphenol-based antioxidant and a phosphite-based antioxidant.

The present invention having the above-described constitution of apolyamide 66 or polyamide 6 resin, a glass fiber and barium sulfate(BaSO₄) having high specific gravity, provides excellent mechanicalproperties, heat resistance and noise and vibration insulationperformance.

According to a further aspect, the present invention provides apartition for a vehicle fabricated of the composition. According tovarious embodiments, such a partition provides a weight reduction effectof about 2.6 kg per one vehicle as compared to a conventional partitionmade of iron. Further, since injection molding can be performed toimplement a complicated shape using the present composition, there is aneffect in that the excellent degree of freedom in design can be ensuredin a narrow space in an engine room.

According to various embodiments, the composition utilizes a bariumsulfate having Moh's hardness of about 3. The use of such a bariumsulfate provides excellent injection moldability, as compared to aconventional polypropylene composition including iron oxide having Moh'shardness of 7.

Other aspects and exemplary embodiments of the invention are discussedinfra.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present invention will now bedescribed in detail with reference to certain exemplary embodimentsthereof illustrated the accompanying drawings which are givenhereinbelow by way of illustration only, and thus are not limitative ofthe present invention, and wherein:

FIG. 1 is a mimetic diagram showing a partition of an engine room of avehicle;

FIG. 2 is a graph showing the magnitude of noise insulated at a left ofa driver's seat for each frequency;

FIG. 3 is a graph showing the magnitude of noise insulated at a right ofthe driver's seat for each frequency;

FIG. 4 is a graph showing the magnitude of noise insulated at a left ofa front passenger seat for each frequency;

FIG. 5 is a graph showing the magnitude of noise insulated at a backseat for each frequency;

FIG. 6 is a graph showing the magnitude of noise insulated at a left ofa VIP seat of the back seat for each frequency;

FIG. 7 is a graph showing the magnitude of noise insulated at a right ofthe VIP seat of the back seat for each frequency;

FIG. 8 is a graph showing the magnitude of noise insulated directlybehind a left engine room for each frequency; and

FIG. 9 is a graph showing the magnitude of noise insulated directlybehind a right engine room for each frequency.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variouspreferred features illustrative of the basic principles of theinvention. The specific design features of the present invention asdisclosed herein, including, for example, specific dimensions,orientations, locations, and shapes will be determined in part by theparticular intended application and use environment.

In the figures, reference numbers refer to the same or equivalent partsof the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

The terms and the words used in the specification and claims should notbe construed with common or dictionary meanings, but construed asmeanings and conception coinciding the spirit of the invention based ona principle that the inventors can appropriately define the concept ofthe terms to explain the invention in the optimum method.

It is understood that the term “vehicle” or “vehicular” or other similarterm as used herein is inclusive of motor vehicles in general such aspassenger automobiles including sports utility vehicles (SUV), buses,trucks, various commercial vehicles, watercraft including a variety ofboats and ships, aircraft, and the like, and includes hybrid vehicles,electric vehicles, plug-in hybrid electric vehicles, hydrogen-poweredvehicles and other alternative fuel vehicles (e.g. fuels derived fromresources other than petroleum). As referred to herein, a hybrid vehicleis a vehicle that has two or more sources of power, for example bothgasoline-powered and electric-powered vehicles.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items.

Unless specifically stated or obvious from context, as used herein, theterm “about” is understood as within a range of normal tolerance in theart, for example within 2 standard deviations of the mean. “About” canbe understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%,0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear fromthe context, all numerical values provided herein are modified by theterm “about”.

Hereinafter, the present invention will be described in detail.

The present invention relates to polyamide resin composition for soundinsulation having excellent mechanical stiffness, heat resistance andnoise insulation function. More specifically, the present inventionrelates to polyamide resin composition which includes a polyamide 66 orpolyamide 6 resin, a glass fiber and barium sulfate (BaSO₄) having highspecific gravity in order to increase mechanical stiffness, heatresistance and injection moldability. According to preferredembodiments, the composition further includes one or more of anantioxidant, a heat resistant stabilizer and/or a lubricant.

To be more specific, it is preferable that the content of the glassfiber is about 15 to 20 parts by weight, the content of barium sulfateis about 45 to 50 parts by weight, the content of the antioxidant isabout 0.3 to 0.5 parts by weight, the content of the heat resistantstabilizer is about 0.3 to 0.5 parts by weight and the content of thelubricant is about 0.2 to 0.4 parts by weight, based on 100 parts byweight of the polyamide 66 or polyamide 6 resin.

Hereinafter, constitution components of the present invention and thecontents thereof will be described in detail.

1. Constitution Component

(1) Polyamide 66 or Polyamide 6

Any polyamide resin known in the art may be used as the polyamide resincomponent. However, it is preferable that polyamide 66 or polyamide 6resin is used. As described herein, the polyamide 66 or polyamide 6resin is a material that is a basis of the present invention. Thepolyamide resin is a material having excellent general mechanical andheat resistance properties such as tensile strength, flexural strength,flexural modulus, heat resistance, chemical resistance, and moldability.As such, the polyamide resin is extensively used in various fields suchas vehicles, airplanes, space and sports.

Further, there are advantageous in that the mechanical and heatresistance properties may be easily improved by including a reinforcingagent, such as a glass fiber, in the polyamide 66 or polyamide 6 resin.

(2) Glass Fiber

The glass fiber functions to improve the mechanical properties of thepolyamide resin composition, such as tensile strength, flexuralstrength, flexural modulus and impact strength, as well as the heatresistance properties, such as a heat distortion temperature (HDT). Anyglass fiber known in the art may be used as the glass fiber. Inaddition, it is preferable that the surface of the glass fiber is coatedwith a silane-based coupling agent in order to increase an interfaceadhesion property between the polyamide resin and the glass fiber.

Herein, it is preferable that the content of the glass fiber is about 15to 20 parts by weight based on 100 parts by weight of polyamide 66 orpolyamide 6. In the case where the content of the glass fiber is lessthan about 15 parts by weight, the mechanical and heat resistanceproperties of the composition may be reduced. On the other hand, in thecase where the content is more than about 20 parts by weight, fluidityof the composition may be reduced to deteriorate the appearance qualityof molded products.

Further, it is preferable that an average diameter of a cross section ofthe glass fiber is about 10 to 13 μm. In the case where the averagediameter of the cross section is less than about 10 μm, since a breakageratio of the glass fiber is high, the mechanical property of thecomposition may be reduced. On the other hand, in the case where theaverage diameter is more than about 13 μm, the appearance quality of thecomposition may be reduced.

Any conventional glass fiber may be used in the present invention.Further, while any length of the glass fiber may be used, it ispreferable that the glass fiber be a long glass fiber such as one havingan average length of about 1 mm to 5 mm in order to improve impactstrength and a dimensional stability effect of the composition. In thecase where the average length of the glass fiber is less than about 1mm, the mechanical and heat resistance properties of the composition maybe reduced and a distortion phenomenon may occur in large-sizedproducts. On the other hand, in the case where the average length ismore than about 5 mm, a significant difference occurs between glassfiber alignment on the surface of the composition and the glass fiberalignment in the composition. This results in a difference in physicalproperties between the surface and the inside of the composition.

According to preferred embodiments, the content of the silane-basedcoupling agent is about 0.1 to 0.3 wt % based on the total weight of theglass fiber. In the case where the content of the silane-based couplingagent is less than about 0.1 wt %, mechanical and heat resistanceproperties of the composition may be reduced. On the other hand, in thecase where the content is more than about 0.3 wt %, moldability may bereduced due to an increase in viscosity of the composition.

(3) Barium Sulfate

Barium sulfate (BaSO₄) is an inorganic filler that improves moldabilityand dimensional stability of the present composition and that furtherincreases specific gravity of the composition, thus improving a soundinsulation property. Since the sound insulation property is generallyincreased in proportion to an increase in specific gravity of thematerial, it is preferable to use a barium sulfate having a highspecific gravity in order to improve the sound insulation property.

Barium sulfate has Moh's hardness of about 3, which is smaller than theMoh's hardness of about 7 for iron oxide used as a conventionalinorganic filler. As such, friction of screws of injection moldingmachines and molds is reduced during an extrusion process and molding ofthe present composition to improve moldability.

It is preferable that the content of barium sulfate is about 45 to 50parts by weight based on 100 parts by weight of polyamide 66 orpolyamide 6. In the case where the content of barium sulfate is lessthan about 45 parts by weight, the specific gravity of the compositionmay be reduced to reduce the sound insulation property. On the otherhand, in the case where the content is more than about 50 parts byweight, appearance quality and physical properties may be reduced.

In addition, it is preferable that the average diameter of the particlesof barium sulfate is about 20 to 30 μm. In the case where the averagediameter is less than about 20 μm, moldability and dimensional stabilitymay be reduced. On the other hand, in the case where the averagediameter is more than about 30 μm, a surface area of barium sulfate isreduced, and effective sound insulation property cannot be obtained.

(4) Antioxidant

The antioxidant functions to suppress a reaction of oxidativedegradation during extrusion and injection processes of the composition.Any conventional antioxidant may be used in the present invention, butit is preferable to use a mixture of a phenol-based antioxidant and aphosphate-based antioxidant.

The phenol-based antioxidant is reacted with radicals generated inplastics to discharge hydrogen in the phenol-based antioxidant, therebystabilizing the radicals, and the antioxidant is converted into theradicals and remains in a stable form through a resonance effect orre-arrangement of electrons.

Any conventional phenol-based antioxidant may be used in the presentinvention, but it is preferable that the phenol-based antioxidant isN,N′-1,6-hexanediylbis(3,5-bis(1,1-dimethylethyl)-4-hydroxybenzene-propaneamideor bis-(3,3-bis-(4′-hydroxy-3′-tetrabutylphenyl)butanoicacid)-glycolester.

Further, the phosphite-based antioxidant performs a function of ahydroperoxide decomposer to prevent the radicals from being generated.Further, if the phosphite-based antioxidant is used together with thephenol-based antioxidant, a synergistic effect can be expected andstability of cross-linked plastics and stability to UV are increased.

Any conventional phosphite-based antioxidant may be used in the presentinvention, but it is preferable that the phosphite-based antioxidant istris-(2,4-di-tertiary-butylphenyl)-phosphite ortetrakis(2,4-di-tertiary-butylphenyl)-4,4′-biphenylene diphosphite.

According to a preferred embodiment, the composition contains about 0.3to 0.5 parts by weight and more preferably 0.4 parts by weight of themixed antioxidant, based on 100 parts by weight of polyamide 66 orpolyamide 6. In the case where the content of the antioxidant is lessthan about 0.3 parts by weight, the antioxidant cannot sufficientlyprevent oxidation, and where the content is more than about 0.5 parts byweight, physical properties and the quality of appearance may bereduced.

(5) Heat Resistant Stabilizer

The heat resistant stabilizer functions to improve heat resistance ofthe composition, and any matter known in the art may be used as the heatresistant stabilizer. According to preferred embodiments, the heatresistant stabilizer is an iodine-based heat resistant stabilizer.According to an exemplary embodiment, the heat resistant stabilizer iscopper iodide (CuI).

The content of the heat resistant stabilizer is preferably about 0.3 to0.5 parts by weight and more preferably about 0.2 parts by weight basedon 100 parts by weight of the polyamide 66 or polyamide 6 resin. In thecase where the content of the heat resistant stabilizer is less thanabout 0.3 parts by weight, the heat resistance properties, such as theheat distortion temperature, of the composition may be reduced. On theother hand, in the case where the content is more than about 0.5 partsby weight, the mechanical properties and the appearance quality may bereduced.

(6) Lubricant

The lubricant functions to adjust friction between the compositions orbetween the composition and a metal when the composition is heated andmolded to improve fluidity and a release property to thereby facilitateprocessing. Any conventional lubricant may be used in the presentinvention, and according to preferred embodiments, an olefine-basedlubricant, more preferably ethylene bisstearamide, is used.

The content of the lubricant is preferably about 0.2 to 0.4 parts byweight and more preferably about 0.2 parts by weight based on 100 partsby weight of the polyamide 66 or polyamide 6 resin. In the case wherethe content of the lubricant is less than about 0.2 parts by weight, thefluidity and the release property may be reduced, and thus it may bedifficult to mold large-sized products. In the case where the lubricantcontent is more than about 0.4 parts by weight, mechanical propertiesand weld strength may be reduced.

2. Use

The present invention provides excellent sounds insulation propertiesand may be applied in various ways so as to provide sound insulation. Inparticular, it is preferred that the present invention is applied to apartition of an engine room of a vehicle.

3. Manufacturing Method

Hereinafter, in another aspect, the present invention relates to amethod of manufacturing a polyamide resin composition for soundinsulation.

The polyamide resin composition for sound insulation may beappropriately manufactured by a person of ordinary skill in the art withreference to known technologies. Specifically, it is preferable that thepolyamide resin composition for sound insulation is manufactured so asto include about 15 to 20 parts by weight of a glass fiber, preferably aglass fiber coated with a silane-based coupling agent, about 45 to 50parts by weight of barium sulfate, about 0.3 to 0.5 parts by weight ofantioxidant, preferably a mixture of a phenol-based antioxidant and aphosphite-based antioxidant, about 0.3 to 0.5 parts by weight of theheat resistant stabilizer and about 0.2 to 0.4 parts by weight of thelubricant, based on 100 parts by weight of the polyamide 66 or polyamide6 resin.

Hereinafter, the present invention will be described in further detailwith reference to examples. It will be obvious to a person havingordinary skill in the art that these examples are illustrative purposesonly and are not to be construed to limit the scope of the presentinvention.

EXAMPLE

FIG. 1 is a mimetic diagram showing the partition 100 of the engine roomof the vehicle which was formed from the polyamide resin compositions ofthe Examples and Comparative Examples. The components and contents ofthe Examples and Comparative Examples are shown in the followingTable 1. Thereafter, physical properties thereof were compared, and setforth in the following Table 2.

TABLE 1 Comparative Example Example Classification Unit 1 2 3 1 2 3Resin Polyamide Part by 100 100 100 — 100 100 66 weight Poly- Part by —— — 100 — — propylene weight Anti- Phenols Part by 0.2 0.2 0.2 0.2 0.20.2 oxidant weight Phosphites Part by 0.2 0.2 0.2 0.2 0.2 0.2 weightHeat resistant Part by 0.5 0.5 0.5 0.5 0.5 0.5 stabilizer weightLubricant Part by 0.3 0.3 0.3 0.3 0.3 0.3 weight Glass fiber (short Partby 15 20 — 25 15 15 fiber) weight Glass fiber (long Part by — — 15 — — —fiber) weight Barium sulfate Part by 50 45 50 — — — (BaSO₄) weight Ironoxide (Fe₂O₃) Part by — — — 50 50 — weight Wollastonite Part by — — — —— 25 weight

Table 1 is a table comparing the components and the contents of theExamples and the Comparative Examples. The antioxidant, the heatresistant stabilizer and the lubricant of the above-described Table 1were included in the same content in the Examples and the ComparativeExamples, and polypropylene was only included in Comparative Example 1.Further, barium sulfate for improving the sound insulation property wasonly included in the Examples (in accordance with the presentinvention), while iron oxide and wollastonite were instead included inthe Comparative Examples (not in accordance with the present invention).

Physical and heat resistance properties of the Examples and theComparative Examples compared through tests, and are described below.

TABLE 2 Test Comparative method Example Example Classification (ASTM)Unit 1 2 3 1 2 3 Specific gravity D792 — 2.06 2.05 2.06 2.15 2.10 1.83Tensile strength D638 MPa 104 122 120 38 100 101 Flexural strength D790MPa 152 166 158 50 150 155 flexural modulus D790 MPa 8620 10200 94005500 9475 9921 Impact strength D256 MPa 45 48 72 31 33 30 (+23□) heatdistortion D648 ° C. 243 243 245 155 242 238 (1.82 MPa)

Table 2 is a table in which physical and heat resistance properties ofthe Examples and the Comparative Examples are numerically representedthrough the specific tests, and compared.

The specific gravity was measured according to ASTM D792, and thetensile strength was measured according to ASTM D638 under the conditionof the temperature of 23±2° C., relative humidity of 50%, atmosphericpressure, and a speed of 5 mm/min.

The flexural strength and the flexural modulus were measured accordingto ASTM D790, and the cross head speed was measured under the conditionof a speed of 5 mm/min.

The impact strength was measured according to ASTM D256 as a valueobtained by dividing energy when the specimen was broken by unitthickness by an Izod notch method at 23±2° C.

The heat distortion temperature was obtained by measuring thetemperature in the case where the specimen was distorted when theambient temperature was increased at the rate of 2° C./min under thecondition of a load of 1.82 MPa on the specimen according to ASTM D648.

According to Table 2, the specific gravity was highest in ComparativeExample 1, but the tensile strength, the flexural strength, the flexuralmodulus and the impact strength were superior in the Examples. Inparticular, one of the most important properties of a compositionapplied to the engine room of the vehicle is heat resistance. Based onthe result that the heat resistance of the Examples was much better thanthe heat resistance of the Comparative Examples, it was demonstratedthat the Examples were better than the Comparative Examples in terms ofthe mechanical and heat resistance properties. Further, it wasdemonstrated that in the case of Example 3 to which the long glass fiberwas applied, all properties were better than Example 1 to which theshort glass fiber was applied.

TABLE 3 400 Hz to 6300 Hz (dB RMS) Left of Left Right Left of Right ofLeft of the the VIP Right of behind behind the the front seat of the VIPthe left the right driver's driver's passenger Back the back seat of theengine engine Classification Unit seat seat seat seat seat back seatroom room Example 3 dB 76 76.4 75.9 78.5 78 78.4 25.2 32.4 No dB 67.867.6 66.9 72.8 72.3 71.3 13.4 13.5 partition Difference dB 8.2 8.8 9 5.75.7 7.1 11.8 18.9

Table 3 is a table in which sound insulation performances of theExamples are compared. After the high-power speaker for tests having thefrequency range of 400 Hz to 6300 Hz was installed in a direction of theinside of the vehicle at a position of the engine of the engine room ofthe vehicle, noise was generated. The insulation of noise by thepartition, to which the present invention was applied, was then measuredby imaging the insulated sound. That is, the magnitude of insulatednoise was increased as the measured numerical value is was increased,and the magnitude of insulated noise was reduced as the measurednumerical value was reduced.

In Table 3, in the case of Example 3 to which the partition was applied,the measured numerical value was higher than that of the case where thepartition was not applied, which means that a large amount of noise isinsulated by the higher numerical value. Accordingly, it was confirmedthat in the case of Example 3 to which the partition was applied, themeasured noise was reduced at all positions in the vehicle and rightbehind the engine room as compared to the case where the partition wasnot applied.

To be more specific, the drawings showing graphs which classify themagnitudes of noise insulated at each position for each frequency inTable 3 are provided below. FIG. 2 is a graph showing the magnitude ofnoise insulated at a left of a driver's seat for each frequency, FIG. 3is a graph showing the magnitude of noise insulated at a right of thedriver's seat for each frequency, FIG. 4 is a graph showing themagnitude of noise insulated at a left of a front passenger seat foreach frequency, FIG. 5 is a graph showing the magnitude of noiseinsulated at a back seat for each frequency, FIG. 6 is a graph showingthe magnitude of noise insulated at a left of a VIP seat of the backseat for each frequency, FIG. 7 is a graph showing the magnitude ofnoise insulated at a right of the VIP seat of the back seat for eachfrequency, FIG. 8 is a graph showing the magnitude of noise insulateddirectly behind a left engine room for each frequency, and FIG. 9 is agraph showing the magnitude of noise insulated directly behind a rightengine room for each frequency. As seen in FIGS. 2 to 9, even thoughthere was a difference between frequencies, from the average values, itwas demonstrated that in the case where the partition was applied (200)a high noise insulation effect was provided as compared to the casewhere the partition was not applied (300) in all graphs.

Further, it was confirmed that in view of only the position of thedriver's seat, the partition of Example 3 (which was in accordance withthe present invention) was positioned between the engine room and thedash board, and thus the noise flowing from the engine room to theposition of the driver's seat was reduced by an average of 8 to 8.8 dB.

The invention has been described in detail with reference to preferredembodiments thereof. However, it will be appreciated by those skilled inthe art that changes or modifications may be made in these embodimentswithout departing from the principles and spirit of the invention, thescope of which is defined in the appended claims and their equivalents.

1. A polyamide resin composition for sound insulation comprising: about15 to 20 parts by weight of a glass fiber, based on 100 parts by weightof polyamide 6.6 or polyamide 6, about 45 to 50 parts by weight ofbarium sulfate, based on 100 parts by weight of the polyamide 6.6 orpolyamide 6 resin, and one or more of about 0.3 to 0.5 parts by weightof an antioxidant, about 0.3 to 0.5 parts by weight of a heat resistantstabilizer, or about 0.2 to 0.4 parts by weight of a lubricant, based on100 parts by weight of the polyamide 6.6 or polyamide 6, wherein anaverage length of the glass fiber is about 1 mm to 5 mm, wherein anaverage diameter of a cross section of the glass fiber is about 10 to 13μm, wherein the glass fiber is coated with a silane-based couplingagent, wherein a weight of the silane-based coupling agent is about 0.1to 0.3 wt % based on a total weight of the glass fiber, wherein anaverage diameter of particles of the barium sulfate is about 20 to 30μm. 2-7. (canceled)
 8. The polyamide resin composition for soundinsulation according to claim 1, the antioxidant comprises a mixture ofa phenol-based antioxidant and a phosphite-based antioxidant.